Room temperature-curable organopolysiloxane composition

ABSTRACT

A room temperature-curable organopolysiloxane composition which does not suffer from surface fissuring even when subjected to external stress (e.g., tensile stress, flexural stress) during the course of its cure was prepared and has a composition of a hydroxyl-terminated polydiorganosiloxane, a hydrophobic silica with a silanol titer not exceeding 2.0 mL, a dry-method silica with a silanol titer of at least 5.0 mL, and an oxime group-containing silane or siloxane.

BACKGROUND OF THE INVENTION

1. Technical Field

This invention relates to a room temperature-curable organopolysiloxanecomposition, and, more particularly, relates to a roomtemperature-curable organopolysiloxane composition which does not sufferfrom fissuring or cracking when its adherend (substrate) undergoesmovement during the course of its cure.

2. Prior Art and Problems to Be Solved by the Invention

Room temperature-curable organopolysiloxane compositions have a numberof excellent properties, and as a result are employed as sealants andadhesives in various fields, for example, in civil engineering andconstruction, in general industry for machinery and tools, and in theelectrical and electronics sectors. A problem associated with this typeof composition is the development of surface fissuring when thecomposition is subjected to external stress (e.g., tensile stress,flexural stress) during the course of its cure.

As a result, the substrate or device carrying the roomtemperature-curable organopolysiloxane composition cannot be moved untilthe composition has undergone some degree of curing and surface skinstrength has developed. This requires a long, disturbance-free holdingperiod.

The present inventors carried out extensive investigations directed atsolving this problem, and as a result they discovered that this problemcan be solved in a single stroke by the addition of a specific type ofhydrophobic silica to room temperature-curable organopolysiloxanecompositions. The present invention was developed based on this finding.

SUMMARY OF THE INVENTION

The present invention takes as its object the introduction of a roomtemperature-curable organopolysiloxane composition which will not sufferfrom surface fissuring even when subjected to external stress (e.g.,tensile stress, flexural stress) during the course of its cure.

The present invention relates to a room temperature-curableorganopolysiloxane composition comprising (A) 100 parts by weight ahydroxyl-terminated polydiorganosiloxane with a viscosity=0.5 to 500Pa.s at 25° C.; (B) 5 to 50 parts by weight hydrophobic silica whosesilanol titer does not exceed 2.0 mL wherein said silanol titer isdetermined as follows: 2.0 g sample is dispersed in a mixture of 25 mLethanol and 75 mL 20 weight % aqueous NaCl, and the quantity of 0.1 Naqueous sodium hydroxide solution required to change the pH of thisdispersion from 4.0 to 9.0 is designated as the silanol titer; (C) 2 to10 parts by weight dry-method silica whose silanol titer is at least 5.0mL wherein said silanol titer is defined in (B); and (D) 0.5 to 25 partsby weight silane or siloxane which contains at least 3 oxime groups ineach molecule.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 and 2 illustrate the method for determining the development ofsurface fissuring in the room temperature-curable organopolysiloxanecomposition. FIG. 1 shows the test set up for measurement of surfacefissuring. FIG. 2 shows a test position after experiencing some stresson the curing room temperature-curable organopolysiloxane composition.

1=adherend wall 1

2=adherend wall 2

3=room temperature-curable organopolysiloxane composition

DETAILED DESCRIPTION OF THE EMBODIMENTS OF THE INVENTION

The polydiorganosiloxane comprising component (A) employed by thepresent invention is the principal or base component of the composition.Its molecular chain terminals must be end-blocked with the hydroxylgroup, and its viscosity at 25° C. must fall within the range of 0.5 to500 Pa.s (Pascal.seconds). This polydiorganosiloxane is exemplified byalpha,omega-dihydroxy polydiorganosiloxanes with the following generalformula HO(R₂ SiO)_(n) H wherein R encompasses substituted andunsubstituted monovalent hydrocarbon groups and each R may be identicalor may differ, and n has a value which provides thispolydiorganosiloxane with a viscosity at 25° C. within the range of 0.5to 500 Pa.s, preferably from 1 to 100 Pa.s. R in the preceding formulaencompass monovalent hydrocarbon groups as exemplified by chain alkylgroups such as methyl, ethyl, isopropyl, hexyl, and octadecyl; alkenylgroups such as vinyl, allyl, and hexenyl; cycloalkyl groups such ascyclohexyl and cyclopentyl; alkaryl groups such as benzyl andbeta-phenylethyl; and aromatic hydrocarbon groups such as phenyl, xenyl,naphthyl, tolyl, and xylyl. R in the preceding formula also encompassesthe substituted hydrocarbon groups which are generated by replacinghydrogen in the aforesaid monovalent hydrocarbon groups with an organicgroup such as beta-cyanoethyl, 3,3,3-trifluoropropyl, andperfluorobutyl. The preferred silanol-terminated polydiorganosiloxane issilanol-terminated polydimethylsiloxane and especially those which havea viscosity of from 1 to 100 Pa.s at 25° C.

The hydrophobic silica comprising the component (B) used by the presentinvention endows the composition according to the present invention withthe unique property to the effect that surface fissuring will not occureven when the composition is subjected to external stress (e.g., tensilestress, flexural stress) during its cure. This hydrophobic silica musthave a silanol titer of no more than 2.0 mL as measured by the silanolquantification method stipulated by the present invention. The silanoltiter as specified by the present invention is determined as follows:2.0 g of the silica (sample) is dispersed in a mixture of 25 mL ethanoland 75 mL 20 weight % aqueous NaCl, and the silanol titer corresponds tothe amount of 0.1N aqueous sodium hydroxide required to change the pH ofthis dispersion from 4.0 to 9.0. This type of hydrophobic silica may beprepared by subjecting the silica micropowders customarily employed asreinforcing fillers for silicone rubber compositions to surfacetreatment with any of various types of hydrophobicizing agents. Saidsilica micropowders are exemplified by dry-method silicas, as typifiedby fumed silica, and by wet-method silicas, as typified by precipitatedsilica. Dry-method silicas are preferred for the present invention. Thehydrophobicizing agents are exemplified by hexamethyldisilazane,trimethylchlorosilane, polyorganohydrogensiloxanes, andpolydimethylsiloxanes. These hydrophobicizing agents act tohydrophobicize the silica micropowder by reacting with the silanolgroups on the surface of the silica micropowder and thus bonding withthe surface of the silica micropowder. In order to treat the surface ofsilica micropowder with such a hydrophobicizing agent, thehydrophobicizing agent may be, for example, added to the silicamicropowder followed by mixing to homogeneity and then heating. Or, thehydrophobicizing agent may be added to the silica micropowder whilestirring and heating the latter.

When heating is carried out in this treatment in the absence of anymixing, the hydrophobicization treatment will not be uniform due to thelow vapor pressures of the hydrophobicizing agents. On the other hand,the structure of the silica micropowder is destroyed and its bulkdensity is increased by extremely vigorous mixing, and the fluidityimprovement afforded by silica micropowder is thereby diminished. Gentlemixing conditions are preferred as a result.

Preferred heating temperatures fall within the range of 100° to 200° C.Moreover, the hydrophobic silica comprising component (B) preferably hasa specific surface area of at least 100 m² /g. This component should beadded at 5 to 50 parts by weight per 100 parts by weight (A), preferablyfrom 5 to 25 parts by weight per 100 parts by weight of (A). Thefunctional effect described above does not appear at less than 5 partsby weight, while the addition of more than 50 parts by weight causes areduction in the extrudability of the room temperature-curableorganpolysiloxane composition according to the present invention fromits storage container.

Through its combined use with the hydrophobic silica of component (B),dry-method silica of component (C) is employed by the present inventionand functions to endow the composition according to the presentinvention with a nonsag character (nonstringing character) while at thesame time providing the composition with the ability to remain free ofsurface fissuring when subjected to external stress during its cure.This dry-method silica must have a silanol titer of at least 5.0 mL. Thedry-method silica under consideration is exemplified by fumed silica,which is produced by the decomposition of silicon tetrachloride, and byarc silica, which is produced by the arc heating of a mixture of quartzsand and coke. Fumed silica is commercially available, for example,under the following tradenames: Aerosil 130, 200, 300, 380, TT-600,MOX-80, and MOX170, from Nippon Aerosil Kabushiki Kaisha (Japan);Cabosil M-5, MS-7, MS-75, HS-7, ET-5, HS-5, and ET-5 from the CabotCorporation (United States); and HDK N20, V15, T30, and T40 from WackerChemie (West Germany). This component should be added at 2 to 10 partsby weight per 100 weight parts component (A). The nonsag character isdiminished at additions less than 2 parts by weight, while the fissuringdescribed above readily occurs when 10 parts by weight is exceeded.

The oxime-containing silane or siloxane of component (D) is employed bythe present invention to function as a crosslinker for the compositionaccording to the present invention. (D) is exemplified bymethyltris(methylethylketoximo)silane,vinyltris(methylethylketoximo)silane,phenyltris(methylethylketoximo)silane,methyltris(diethylketoximo)silane, tetrakis(methylethylketoximo)silane,and the partial hydrolyzates of the preceding. The amount of silane orsiloxane of component (D) is from 0.5 to 25 parts by weight per 100parts by weight of (A). Preferably, (D) is present in an amount of from1 to 20 parts by weight per 100 parts by weight of (A). The preferred(D) are vinyltris(methylethylketoximo)silane,methyltris(methylethylketoximo)silane, and mixtures thereof.

The room temperature-curable organopolysiloxane composition according tothe present invention comprises components (A) through (D) as describedherein, but in a preferred execution it additionally contains anorganoalkoxysilane, component (E), which is an epoxy-containingorganoalkoxysilane, an amino-containing organoalkoxysilane, or areaction product of the epoxy-containing organoalkoxysilane and theamino-containing organoalkoxysilane. The epoxy-containingorganoalkoxysilanes are exemplified bygamma-glycidoxypropyltrimethoxysilane andbeta-(3,4-epoxycyclohexyl)ethyltrimethoxysilane. The amino-containingorganoalkoxysilanes are exemplified bygamma-aminopropyltrimethoxysilane, gamma-aminopropyltriethoxysilane, andN-beta-(aminoethyl)-gamma-aminopropyltrimethoxysilane; and by theirpartial hydrolyzates and reaction products. The aforesaid reactionproduct is prepared by reacting a mixture of epoxy-containingorganoalkoxysilane and amino-containing organoalkoxysilane at roomtemperature or with heating.

Component (E) provides the composition according to the presentinvention with adhesiveness for various types of substrates while at thesame time further enhancing the composition's ability to remain free ofsurface fissuring when subjected to external stress (e.g., tensilestress, flexural stress) during its cure. Component (E) is added at 0.5to 10 parts by weight per 100 weight parts component (A), preferablyfrom 0.5 to 5 parts by weight.

The composition according to the present invention may optionallycontain, component (F), a catalyst in order to accelerate its cure.Typical catalysts in this regard are lead 2-ethyloctoate, dibutyltindiacetate, dibutyltin 2-ethylhexoate, dibutyltin dilaurate, butyltintri-2-ethylhexoate, and dibutyltin acetylacetonate. The preferredcatalysts are dialkyltin dicarboxylates, such as dibutyltin dilaurate,dibutyltin 2-ethylhexoate, and dibutyltin diacetate. Component (F) isadded at 0.001 to 10 parts by weight, preferably 0.01 to 5 parts byweight per 100 parts by weight of (A).

The composition according to the present invention is prepared simply bymixing components (A) through (D) or components (A) through (E),optionally along with the cure-accelerating catalyst (F). Thecomposition according to the present invention may also contain thoseadditives already known for application with room temperature-curableorganopolysiloxane compositions insofar as the object of the presentinvention is not impaired. Examples in this regard are the variousorganic solvents; fluidity adjuster such as low-molecular-weightorganopolysiloxane, illustrated by silanol-terminatedpoly(dimethylsiloxane-co-phenylmethylsiloxane) having a viscosity ofless than 0.1 Pa.s at 25° C.; various types of fillers and pigments suchas magnesium oxide, alumina, zinc oxide, and iron oxide; flameretardants such as manganese carbonate; heat stabilizers such as ceriumhydroxide and cerium oxide; and adhesion promoters such as silanecoupling agents.

The present invention is explained in greater detail below throughillustrative examples. In the examples and comparison examples,parts=parts by weight, and the viscosity is the value measured at 25° C.The properties were measured using the following test methods.

EXTRUDABILITY

The room temperature-curable organopolysiloxane composition was filledinto a 2 mL (milliliter) syringe, and the time required to extrude theentire quantity of the composition using a pressure of 2 kg/cm² isreported in seconds.

RUBBER PROPERTIES

The room temperature-curable organopolysiloxane composition was cured atroom temperature for 7 days in order to produce a 3 mm-thick siliconerubber sheet, and the physical properties (hardness, tensile strength,elongation) of this silicone rubber sheet were measured in accordancewith JIS K 6301.

MEASUREMENT OF SURFACE FISSURING

In order to measure surface fissuring, the room temperature-curableorganopolysiloxane composition 3 was applied between adherend wall 1 andadherend wall 2 in the test set-up depicted in FIG. 1. Then, after thespecified period of time, adherend wall 2 was moved while holdingadherend wall 1 stationary (as shown in FIG. 2) until the angle betweenadherend wall 1 and adherend wall 2 was 180 degrees. The surface of theroom temperature-curable organopolysiloxane composition 3 was theninspected using a magnifying glass for the presence of fissuring orcracking.

EXAMPLE 1

A base was prepared by mixing to homogeneity into 100 parts alpha,omega-dihydroxy polydimethylsiloxane with viscosity=13 Pa.s: 14.3 partshydrophobic silica with silanol titer=0.81 mL and specific surfacearea=200 m² /g (prepared by hydrophobicizing the surface of dry-methodsilica by treatment with hexamethyldisilazane); 5.7 parts dry-methodsilica (non-hydrophobicized) with silanol titer=9.11 mL and specificsurface area=200 m² /g; and 2.1 parts silanol-terminatedpoly(dimethylsiloxane-co-methylphenylsiloxane) with viscosity=10⁻⁵ m² /s(fluidity adjuster).

100 Parts of the base thus obtained was mixed to homogeneity whileexcluding moisture with 4.6 parts vinyltris(methylethylketoximo)silane,3.0 parts methyltris(methylethylketoximo)silane, 1.5 partsgamma-glycidoxypropyltrimethoxysilane, and 0.3 part dibutyltin dilaurateto form a single-package room temperature-curable organopolysiloxanecomposition. This composition was sealed into aluminum tubes.

This composition was subsequently investigated with regard toextrudability, appearance of surface fissures, and post-cure rubberproperties (hardness, tensile strength, and elongation), and the resultswere as reported in the Table.

EXAMPLE 2

A base was prepared by mixing to homogeneity into 100 partsalpha,omega-dihydroxypolydimethylsiloxane with viscosity=12 Pa.s: 14.3parts hydrophobic silica with silanol titer=1.20 mL and specific surfacearea=200 m² /g (prepared by hydrophobicizing the surface of dry-methodsilica by treatment with hexamethyldisilazane) and 5.7 parts dry-methodsilica (non-hydrophobicized) with silanol titer=9.11 mL and specificsurface area=200 m² /g.

100 Parts of the base thus obtained was mixed to homogeneity whileexcluding moisture with 7.6 parts vinyltris(methyl ethylketoxime)silane, 1.5 partsN-beta(aminoethyl)-gamma-aminopropyltrimethoxysilane, and 0.3 partdibutyltin dilaurate to form a single-package room temperature-curableorganopolysiloxane composition. This composition was sealed intoaluminum tubes. The composition was subsequently investigated withregard to extrudability, appearance of surface fissures, and post-curerubber properties (hardness, tensile strength, and elongation), and theresults were as reported in the Table.

EXAMPLE 3

A base was prepared by mixing to homogeneity into 100 partsalpha,omega-dihydroxy polydimethylsiloxane with viscosity =13 Pa.s: 10.7parts hydrophobic silica with silanol titer=0.38 mL and specific surfacearea=100 m² /g (prepared by hydrophobicizing the surface of dry-methodsilica by treatment with dimethylpolysiloxane with viscosity=100centistokes), 3.6 parts dry-method silica (non-hydrophobicized surface)with silanol titer=8.55 mL and specific surface area=200 m² /g, and 3.1parts silanol-terminated poly(dimethylsiloxane-comethylphenylsiloxane)with viscosity=10⁻⁵ m² /s (fluidity adjuster).

100 Parts of the base thus obtained was mixed to homogeneity whileexcluding moisture with 4.6 parts vinyltris(methylethylketoximo)silane,3.0 parts methyltris(methylethylketoximo)silane, 1.5 partsN-beta(aminoethyl)-gamma-aminopropyltrimethoxysilane, and 0.3 partdibutyltin dilaurate to form a single-package room temperature-curableorganopolysiloxane composition. This composition was sealed intoaluminum tubes.

This composition was subsequently investigated with regard toextrudability, appearance of surface fissures, and post-cure rubberproperties (hardness, tensile strength, and elongation), and the resultswere as reported in the Table.

COMPARISON EXAMPLE 1

A single-package room temperature-curable organopolysiloxane compositionwas prepared as in Example 1, but in the present case using dry-methodsilica with silanol titer=9.11 mL in place of the hydrophobic silicawith silanol titer=0.81 mL used in Example 1. The properties of thiscomposition were measured as in Example 1, and the results were asreported in the Table.

COMPARISON EXAMPLE 2

A single-package room temperature-curable organopolysiloxane compositionwas prepared as in Example 1, but in the present case using ahydrophobic silica with silanol titer=3.63 mL and specific surfacearea=200 m² /g (prepared by the hydrophobicization of the surface ofdry-method silica by treatment with methyltrichlorosilane) in place ofthe hydrophobic silica with silanol titer=0.81 mL used in Example 1. Theproperties of this composition were measured as in Example 1, and theresults were as reported in the Table.

COMPARISON EXAMPLE 3

A room temperature-curable composition was prepared as described inExample 1, except for replacing the dry process silica having a titer of9.11 mL with the hydrophobic silica having a titer of 0.81 mL. Thecomposition was evaluated as described in Example 1, and the resultswere as shown in the Table. This composition exhibited stringing whereasthe composition of Example 1 did not exhibit any stringing.

                                      TABLE                                       __________________________________________________________________________            Example                                                                            Example                                                                             Example                                                                            Comp.                                                                             Comp.                                                                             Comp.                                         PROPERTIES                                                                            1    2     3    Ex. 1                                                                             Ex. 2                                                                             Ex. 3                                         __________________________________________________________________________    Extrud- 40   47    47   72  71  29                                            ability                                                                       (sec/mL)                                                                      Surface                                                                       fissuring                                                                     test                                                                          (see note 1)                                                                  after   +    +     +    +   +   +                                             1 minute                                                                      10 minutes                                                                            +    +     +    x   x   +                                             20 minutes                                                                            +    +     +    x   x   +                                             30 minutes                                                                            +    +     +    x   x   +                                             40 minutes                                                                            +    +     +    +   +   +                                             Post-cure                                                                     properties                                                                    Hardness,                                                                             37   38    31   36  37  25                                            JIS-A                                                                         Tensile 31   32    22   26  30  30                                            strength                                                                      (kg/cm2)                                                                      Elongation,                                                                           430  400   340  320 410 460                                           __________________________________________________________________________     note:                                                                         + = no appearance of surface fissuring                                        x = appearance of surface fissuring                                      

EFFECTS OF THE INVENTION

Because the room temperature-curable organopolysiloxane compositionaccording to the present invention is composed of components (A) through(D) or (A) through (E), and in particular because it contains specificquantities of both the particular type of hydrophobic silica comprisingcomponent (B) and the particular type of dry-method silica comprisingcomponent (C), it characteristically will not develop surface fissuringeven when subjected to external stress (e.g., tensile stress, flexuralstress) during the course of its cure.

That which is claimed is:
 1. A room temperature-curableorganopolysiloxane composition comprising(A) 100 parts by weight ahydroxyl-terminated polydiorganosiloxane with a viscosity=0.5 to 500Pa.s at 25° C.; (B) 5 to 50 parts by weight hydrophobic silica whosesilanol titer does not exceed 2.0 mL wherein said silanol titer isdetermined as follows: 2.0 g sample is dispersed in a mixture of 25 mLethanol and 75 mL 20 weight % aqueous NaCl, and the quantity of 0.1Naqueous sodium hydroxide solution required to change the pH of thisdispersion from 4.0 to 9.0 is designated as the silanol titer; (C) 2 to10 parts by weight dry-method silica whose silanol titer is at least 5.0mL wherein said silanol titer is defined in (B); and (D) 0.5 to 25 partsby weight silane or siloxane which contains at least 3 oxime groups ineach molecule.
 2. The room temperature-curable organopolysiloxanecomposition according to claim 1 further comprising(E) 0.5 to 10 partsby weight parts of an organoalkoxysilane selected from the groupconsisting of epoxy-containing organoalkoxysilane, amino-containingorganoalkoxysilane, and a reaction mixture thereof.
 3. The roomtemperature-curable organopolysiloxane composition according to claim 1further comprising(F) a catalyst to accelerate the cure.
 4. The roomtemperature-curable organopolysiloxane composition according to claim 3further comprising(F) a catalyst to accelerate the cure.
 5. The roomtemperature-curable organopolysiloxane composition according to claim 1in which the polydiorganosiloxane of (A) is polydimethylsiloxane whichhas a viscosity of 1 to 100 Pa.s, (B) is present in an amount of from 5to 25 parts by weight per 100 parts by weight of (A), and (D) is presentin an amount of from 1 to 20 parts by weight per 100 parts by weight of(A).
 6. The room temperature-curable organopolysiloxane compositionaccording to claim 2 in which the polydiorganosiloxane of (A) ispolydimethylsiloxane which has a viscosity of 1 to 100 Pa.s, (B) ispresent in an amount of from 5 to 25 parts by weight per 100 parts byweight of (A), (D) is present in an amount of from 1 to 20 parts byweight per 100 parts by weight of (A), and (E) is present in an amountof from 0.5 to 5 parts by weight per 100 parts by weight of (A).
 7. Theroom temperature-curable organopolysiloxane composition according toclaim 3 in which the polydiorganosiloxane of (A) is polydimethylsiloxanewhich has a viscosity of 1 to 100 Pa.s, (B) is present in an amount offrom 5 to 25 parts by weight per 100 parts by weight of (A), (D) ispresent in an amount of from 1 to 20 parts by weight per 100 parts byweight of (A), and (F) is present in an amount of from 0.001 to 10 partsby weight per 100 parts by weight of (A).
 8. The roomtemperature-curable organopolysiloxane composition according to claim 7in which (F) is present in an amount of from 0.01 to 5 parts by weightper 100 parts by weight of (A).
 9. The room temperature-curableorganopolysiloxane composition according to claim 4 in which thepolydiorganosiloxane of (A) is polydimethylsiloxane which has aviscosity of 1 to 100 Pa.s, (B) is present in an amount of from 5 to 25parts by weight per 100 parts by weight of (A), (D) is present in anamount of from 1 to 20 parts by weight per 100 parts by weight of (A),and (E) is present in an amount of from 0.5 to 5 parts by weight per 100parts by weight of (A), and (F) is present in an amount of from 0.01 to5 parts by weight per 100 parts by weight of (A).
 10. The roomtemperature-curable organopolysiloxane composition according to claim 1in which (D) is a silane selected from the group consisting ofvinyltris(methylethylketoximo)silane,methyltris(methylethylketoximo)silane, and mixtures thereof.
 11. Theroom temperature-curable organopolysiloxane composition according toclaim 5 in which (D) is a silane selected from the group consisting ofvinyltris(methylethylketoximo)silane,methyltris(methylethylketoximo)silane, and mixtures thereof.
 12. Theroom temperature-curable organopolysiloxane composition according toclaim 8 in which (D) is a silane selected from the group consisting ofvinyltris(methylethylketoximo)silane,methyltris(methylethylketoximo)silane, and mixtures thereof.
 13. Theroom temperature-curable organopolysiloxane composition according toclaim 9 in which (D) is a silane selected from the group consisting ofvinyltris(methylethylketoximo)silane,methyltris(methylethylketoximo)silane, and mixtures thereof.
 14. Theroom temperature-curable organopolysiloxane composition according toclaim 13 in which the silane of (D) isvinyltris(methylethylketoximo)silane.
 15. The room temperature-curableorganopolysiloxane composition according to claim 13 in which the silaneof (D) is a mixture of vinyltris(methylethylketoximo)silane andmethyltris(methylethylketoximo)silane.
 16. The room temperature-curableorganopolysiloxane composition according to claim 15 in which theorganoalkoxysilane of (E) is gamma-glycidoxypropyltrimethoxysilane. 17.The room temperature-curable organopolysiloxane composition according toclaim 14 in which the organoalkoxysilane of (E) isN-beta-(aminoethyl)-gamma-aminopropyltrimethoxysilane.
 18. The roomtemperature-curable organopolysiloxane composition according to claim 15in which the organoalkoxysilane of (E) isN-beta-(aminoethyl)-gamma-aminopropyltrimethoxysilane.
 19. The roomtemperature-curable organopolysiloxane composition according to claim 16further comprising a fluidity adjuster.
 20. The room temperature-curableorganopolysiloxane composition according to claim 19 in which thefluidity adjuster is a silanol-terminatedpoly(dimethylsiloxane-comethylphenylsiloxane) having a viscosity of lessthan 0.1 Pa.s at 25° C.